Re: [APML]: Image Registration

[Maxx <a0011306@airmail.net>]

The Astro-Photography Mailing List
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Chuck Vaughn wrote:
> 
> The Astro-Photography Mailing List
> ------------------------------------
> 
> Jerry,
> 
> Just from the causes you've listed it seems unlikely that they can
> all be controlled to the degree we'd like them to be. A better
> alignment tool is probably the only answer.

  Maxx wrote,
> 
  There is another possibility. Film hypered to very high vacuum
  levels absorbs more moisture during long exposures. This can
induce      some warpage or stretching of the negative causing the same
image
  to be slightly distorted from one negative to the other.
Flowing         nitrogen thru the camera during exposure may help
prevent film
  distortion or buckling.
  Tony Hallas uses a 12" Newtonian and a refractor and aligns the negs
  from both with picture window, no mention of alignment problems.
He     also flows nitrogen during exposures.



> If you or anyone else would like to wrestle with the images I've been,
> I could upload the full res jpegs of Robert's green and blue Veil
> exposures for you to try. These are the ultimate in bad. I had far
> better luck aligning my blue and green Pelican refractor exposures
> to my 500mm lens red Pelican exposure! I've never seen anything as
> bizarre as these.
> 
> Chuck
>